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  • Add Method to Built In Class

    - by Evorlor
    I am pretty sure this is not doable, but I will go ahead and cross my fingers and ask. I am trying to add a method to a built in class. I want this method to be callable by all of the built in class's subclasses. Specifically: I have a JButton, a JTextPane, and other JComponents. I want to be able to pass in a JDom Element instead of a Rectangle to setBounds(). My current solution is to extend each JComponent subclass with the desired methods, but that is a LOT of duplicate code. Is there a way I can write the following method just one time, and have it callable on all JComponent objects? Or is it required that I extend each subclass individually, and copy and paste the method below? public void setBounds(Element element) { this.setBounds(Integer.parseInt(element.getAttribute( "x").toString()), Integer.parseInt(element .getAttribute("y").toString()), Integer .parseInt(element.getAttribute("width").toString()), Integer.parseInt(element.getAttribute("height") .toString())); }

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  • Are static members inherited? (C++)

    - by Keand64
    When static members are inherited, are they static for the entire heirarchy, or just that class, ie: class SomeClass { public: SomeClass(){total++;} static int total; }; class SomeDerivedClass: public SomeClass { public: SomeDerivedClass(){total++;} }; int main() { SomeClass A; SomeClass B; SomeDerivedClass C; return 0; } would total be 3 in all three instances, or would it be 2 for SomeClass and 1 for SomeDerivedClass?

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  • Problem with inherited classes in C#

    - by Unniloct
    I have a class called "Entity," with two child classes: "Creature" and "Item." (I'm making a game.) Creature has two functions called "Attack," one for attacking Creatures, and one for attacking Items. So far, everything works well. Now I'm working on the shooting bit, so I have a function called SelectTarget(). It takes all of the Entities (both Creatures and Items) in the player's view that the player can shoot and lets the player choose one. So here lies the problem: SelectTarget() returns an Entity, but I need some code to figure out whether that Entity is a Creature or an Item, and process it appropriately. Since this question looks kind of empty without any code, and I'm not 100% sure my explanation is good enough, here's where I'm at: if (Input.Check(Key.Fire)) { Entity target = Game.State.SelectTarget.Run(); this.Draw(); if (target != null) { //Player.Attack(target); // This won't work, because I have: // Player.Attack((Creature)Target) // Player.Attack((Item)Target) // but nothing for Entity, the parent class to Creature and Item. return true; } } (If the way the game is laid out seems weird, it's a roguelike.)

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  • unable to pas derived List<>

    - by Tarscher
    Hi all, I have class A {} class B : A {} I also have a method that expects a List parameter void AMethod(List<A> parameter) {} Why can't I List<B> bs = new List<B>(); AMethod(bs); And secondly what is the most elegant way to make this work? regards

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  • C# Why does code compile fine when there is an ambiguous virtual method?

    - by Jimbo
    I have a class (Class B) that inherits another class (Class A) that contains virtual methods. Mistakenly, I omitted the override keyword when declaring a (supposed to be) overriding method in Class B. Class A public class ClassA{ public virtual void TestMethod(){ } } Class B public class ClassB : ClassA{ public void TestMethod(){ } } The code compiled without a problem. Can anyone explain why?

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  • C++ - Error: expected unqualified-id before ‘using’

    - by Francisco P.
    Hello, everyone. I am having some trouble on a project I'm working on. Here's the header file for the calor class: #ifndef _CALOR_ #define _CALOR_ #include "gradiente.h" using namespace std; class Calor : public Gradiente { public: Calor(); Calor(int a); ~Calor(); int getTemp(); int getMinTemp(); void setTemp(int a); void setMinTemp(int a); void mostraSensor(); }; #endif When I try to compile it: calor.h|6|error: expected unqualified-id before ‘using’| Why does this happen? I've been searching online and learned this error occurs mostly due to corrupted included files. Makes no sense to me, though. This class inherits from gradiente: #ifndef _GRADIENTE_ #define _GRADIENTE_ #include "sensor.h" using namespace std; class Gradiente : public Sensor { protected: int vActual, vMin; public: Gradiente(); ~Gradiente(); } #endif Which in turn inherits from sensor #ifndef _SENSOR_ #define _SENSOR_ #include <iostream> #include <fstream> #include <string> #include "definicoes.h" using namespace std; class Sensor { protected: int tipo; int IDsensor; bool estadoAlerta; bool estadoActivo; static int numSensores; public: Sensor(/*PARAMETROS*/); Sensor(ifstream &); ~Sensor(); int getIDsensor(); bool getEstadoAlerta(); bool getEstadoActivo(); void setEstadoAlerta(int a); void setEstadoActivo(int a); virtual void guardaSensor(ofstream &); virtual void mostraSensor(); // FUNÇÃO COMUM /* virtual int funcaoComum() = 0; virtual int funcaoComum(){return 0;};*/ }; #endif For completeness' sake, here's definicoes.h #ifndef _DEFINICOES_ #define _DEFINICOES_ const unsigned int SENSOR_MOVIMENTO = 0; const unsigned int SENSOR_SOM = 1; const unsigned int SENSOR_PRESSAO = 2; const unsigned int SENSOR_CALOR = 3; const unsigned int SENSOR_CONTACTO = 4; const unsigned int MIN_MOVIMENTO = 10; const unsigned int MIN_SOM = 10; const unsigned int MIN_PRESSAO = 10; const unsigned int MIN_CALOR = 35; #endif Any help'd be much appreciated. Thank you for your time. Thanks for your time!

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  • WPF inherited UserControl lost VS designer support

    - by PaN1C_Showt1Me
    Hi ! I' written this UserControl: <my:MyUserControl x:Class="MyClass" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:my="clr-namespace:MyNameSpace.MyControls;assembly=MyAssembly"> </my:MyUserControl> public partial class Editor : MyNameSpace.MyControls.MyUserControl {} Everything works, the control is shown in the VS 2008 Designer, but I cannot click directly in the elements and select them as it was with UserControl. Any idea how to solve it?

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  • Hibernate subclass with foreign key relationships

    - by shikarishambu
    I need some help defining the following object hierarchy/ database relationship in Hibernate From the object sense – Agent is inherited from Person and Agency is inherited from Organization. they are inherited from Party which can have multiple Addresses associated with it The database consists of Agent - ID - Name -PartyID (references Party.ID) Agency -ID -Name -PartyID (references Party.ID) Address -AddrID -PartyID (references Party.ID) -Street Party. -PartyID

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  • Can I make a derived class inherit a derived member from its base class in Java?

    - by Eric
    I have code that looks like this: public class A { public void doStuff() { System.out.print("Stuff successfully done"); } } public class B extends A { public void doStuff() { System.out.print("Stuff successfully done, but in a different way"); } public void doMoreStuff() { System.out.print("More advanced stuff successully done"); } } public class AWrapper { public A member; public AWrapper(A member) { this.member = member; } public void doStuffWithMember() { a.doStuff(); } } public class BWrapper extends AWrapper { public B member; public BWrapper(B member) { super(member); //Pointer to member stored in two places: this.member = member; //Not great if one changes, but the other does not } public void doStuffWithMember() { member.doMoreStuff(); } } However, there is a problem with this code. I'm storing a reference to the member in two places, but if one changes and the other does not, there could be trouble. I know that in Java, an inherited method can narrow down its return type (and perhaps arguments, but I'm not certain) to a derived class. Is the same true of fields?

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  • Should I share UI for objects that use common fields?

    - by wb
    I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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  • Calling child constructor by casting (ChildClass)parentObject; to track revisions

    - by FreshCode
    To track revisions of a Page class, I have a PageRevision class which inherits from Page and adds a revision ID (Guid RevisionID;). If possible, how should I cast an existing Page object to a PageRevision and ensure that the PageRevision constructor is called to create a new revision ID? I could could have a PageRevision(Page page) constructor which generates the Guid and copies all the Page attributes, but I want to automate it, especially if a Page class has many attributes (and I later add one, and forget to modify the copy constructor). Desired use Page page = new Page(123, "Page Title", "Page Body"); // where 123 is page ID PageRevision revision = (PageRevision)page; // now revision.RevisionID should be a new Guid. Page, PageRevision classes: public class Page { public int ID { get; set; } public string Title { get; set; } public string Body { get; set; } } public class PageRevision : Page { public Guid RevisionID { get; set; } public PageRevision() { this.RevisionID = Guid.NewGuid(); } }

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • PHP class extends not working why and is this how to correctly extend a class?

    - by Matthew
    Hi so I'm trying to understand how inherteince works in PHP using object oriented programming. The main class is Computer, the class that is inheriting is Mouse. I'm extedning the Computer class with the mouse class. I use __construct in each class, when I istinate the class I use the pc type first and if it has mouse after. For some reason computer returns null? why is this? class Computer { protected $type = 'null'; public function __construct($type) { $this->type = $type; } public function computertype() { $this->type = strtoupper($this->type); return $this->type; } } class Mouse extends Computer { protected $hasmouse = 'null'; public function __construct($hasmouse){ $this->hasmouse = $hasmouse; } public function computermouse() { if($this->hasmouse == 'Y') { return 'This Computer has a mouse'; } } } $pc = new Computer('PC', 'Y'); echo $pc->computertype; echo $pc->computermouse;

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  • [PHP] How to unset object's inherited properties ?

    - by vbklv
    I have an Object ( [id] => 1 [parent_id] => 0 [result:Database:private] => [db:Database:private] => mysqli Object ( [affected_rows] => 0 ... ) ) Obviously, the Object has inherited the 'db' and 'result' properties of the parent Database class. unset($object-result) nor unset($object-result:Database) nor unset($object-result:Database:private) work. How could I unset those properties when they are no longer needed (i.e. when the object properties are about to be output)? Is it a generally a good idea to have a database object as an inherited property of other classes (extend one Database class with all other classes that use database connections)?

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  • Implement two functions with the same name but different, non-covariant return types due to multiple abstract base classes

    - by user1508167
    If I have two abstract classes defining a pure virtual function with the same name, but different, non-covariant return types, how can I derive from these and define an implementation for both their functions? #include <iostream> class ITestA { public: virtual ~ITestA() {}; virtual float test() =0; }; class ITestB { public: virtual ~ITestB() {}; virtual bool test() =0; }; class C : public ITestA, public ITestB { public: /* Somehow implement ITestA::test and ITestB::test */ }; int main() { ITestA *a = new C(); std::cout << a->test() << std::endl; // should print a float, like "3.14" ITestB *b = dynamic_cast<ITestB *>(a); if (b) { std::cout << b->test() << std::endl; // should print "1" or "0" } delete(a); return 0; } As long as I don't call C::test() directly there's nothing ambiguous, so I think that it should work somehow and I guess I just didn't find the right notation yet. Or is this impossible, if so: Why?

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  • Constructors from extended class in Java

    - by Crystal
    I'm having some trouble with a hw assignment. In one assignment, we had to create a Person class. Mine was: public class Person { String firstName; String lastName; String telephone; String email; public Person() { firstName = ""; lastName = ""; telephone = ""; email = ""; } public Person(String firstName) { this.firstName = firstName; } public Person(String firstName, String lastName, String telephone, String email) { this.firstName = firstName; this.lastName = lastName; this.telephone = telephone; this.email = email; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getTelephone() { return telephone; } public void setTelephone(String telephone) { this.telephone = telephone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public boolean equals(Object otherObject) { // a quick test to see if the objects are identical if (this == otherObject) { return true; } // must return false if the explicit parameter is null if (otherObject == null) { return false; } if (!(otherObject instanceof Person)) { return false; } Person other = (Person) otherObject; return firstName.equals(other.firstName) && lastName.equals(other.lastName) && telephone.equals(other.telephone) && email.equals(other.email); } public int hashCode() { return 7 * firstName.hashCode() + 11 * lastName.hashCode() + 13 * telephone.hashCode() + 15 * email.hashCode(); } public String toString() { return getClass().getName() + "[firstName = " + firstName + '\n' + "lastName = " + lastName + '\n' + "telephone = " + telephone + '\n' + "email = " + email + "]"; } } Now we have to extend that class and use that class in our constructor. The function protoype is: public CarLoan(Person client, double vehiclePrice, double downPayment, double salesTax, double interestRate, CAR_LOAN_TERMS length) I'm confused on how I use the Person constructor from the superclass. I cannot necessarily do super(client); in my constructor which is what the book did with some primitive types in their example. Not sure what the correct thing to do is... Any thoughts? Thanks!

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  • templated class : accessing derived normal-class methods

    - by user1019129
    I have something like this : class Container1 { public: method1() { ... } } class Container2 { public: method1() { ... } } template<class C = Container1> class X : public C { public: using C::method1(); ..... X(string& str) : C(str) {}; X& other_method() { method1(); ...; } } My question is why I have to use "using C::method1()", to be able to access the method.. Most of answers I found is for the case where templated-class inhering templated-class. Normally they mention using "this-", but this does not seem to work in this case. Can I do something else shorter... Also I'm suspecting the other error I'm getting is related to the same problem : no match call for (X<Container1>) (<std::string&>)

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  • How do I inherit abstract unit tests in Ruby?

    - by Graeme Moss
    I have two unit tests that should share a lot of common tests with slightly different setup methods. If I write something like class Abstract < Test::Unit::TestCase def setup @field = create end def test_1 ... end end class Concrete1 < Abstract def create SomeClass1.new end end class Concrete2 < Abstract def create SomeClass2.new end end then Concrete1 does not seem to inherit the tests from Abstract. Or at least I cannot get them to run in eclipse. If I choose "Run all TestCases" for the file that contains Concrete1 then Abstract is run even though I do not want it to be. If I specify Concrete1 then it does not run any tests at all! If I specify test_1 in Concrete1 then it complains it cannot find it ("uncaught throw :invalid_test (ArgumentError)"). I'm new to Ruby. What am I missing here?

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  • Is there any difference these two pieces of code?

    - by Poiuyt
    #include<stdio.h> class A {public: int a; }; class B: public A {private: int a;}; int main(){ B b; printf("%d", b.a); return 0; } #include<stdio.h> class A {public: int a; }; class B: private A {}; int main(){ B b; printf("%d", b.a); return 0; } I ask because I get different errors: error: 'int B::a' is private error: 'int A::a' is inaccessible Apart from what the errors might reveal, is there any difference at all in the behaviour of these two pieces of code?

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  • Java : Using parent class method to access child class variable

    - by Jayant
    I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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